I'm doing a budget build on my daily driver.  Can anyone reccomend a good dished piston that would allow me to run 64cc Vortec heads on a standard-bore SBC 400 and keep compression low enough for 91 octane?  

You could use the Ross 99531, but they are expensive at just over $600 per set of 8. They have a 20cc dish. Assuming 0.010 deck to piston, 4.2 Bore x 0.040 thickness head gasket, this will give about 9.5:1 Compression Ratio

If you're looking to use a hypereutectic piston, take a look at a Keith Black D-shaped dish piston. You can find a 22cc dish or a 18cc dish depending on if you have 5.7" or 6" connecting rods.

PN KB168 - 22cc dish, 5.7 rod
PN KB147 - 18cc dish, 5.7 rod
PN KB130 - 18cc dish, 6.0 rod

In this day and age of $3.00+ gas prices, for a daily driver, perhaps you would consider a lower compression so you can use the low octane gas.

The KB126 - 30cc D-dish, 5.7 rod  $260/ set

 .005 deck, .039 head gasket, 64cc  = 9.03 : 1  compression

The Vortec head is pretty tolerant of lower octane fuel. As they came in 96 with about 9.1 to 1 compression, the engines were rated to operate on 87 octane. This, however, was with port injection which improves an engine's resistance to detonation compared to carburation or TBI injection.

The Keith Black pistons that Gib listed are just what you want for a non-competition engine run on the street.

Keeping intake air temp as low as possible is a great aid for limiting detonation. Therefore, picking up an air source from somewhere other than under the hood is important. That of course means that you don't use anything other than the factory style enclosed air cleaner with a snorkel. Open sided air cleaners and things like the K&N breathing top cover are determental to power and detonation resistance. This is because they allow the hot under hood air into the engine. For every 10 degrees F above 60 degrees F the engine looses 1% of its power. So if the under hood temp is 160 degrees, the engine losses 10% power compared to if it was sourcing outside air at 60 degrees. Of course in the real world underhood temps are closer to 190-200 degrees. So a stock type boxed air cleaner with a hose to a location behind the grill but not the radiator is the best solution for a street vehicle. There are some limits as to how nuts you can get here as a carburated or TBI injected engine does depend upon heat to help evaporate the fuel into a mixture with the incoming air. So a street engine that spends most of its life at cruise RPMs needs some heat. At high RPM natural turbulance will keep things mixed up. But a cruise there isn't enough of this action to thorughly mix the fuel and air. The Vortec head does not use an exhaust heat cross over that the factory typically utilizes to force evaporation, but it does flow coolant, which is sufficient when the engine is warm. But if you live in a cold climate, you may have smoothness issues till the engine warms up. One way around that is to use the factory style air-cleaner that sources hot air off the exhaust manifold when the engine is first started.

If you need more breathing capacity than offered by a paper air filter element  then use a K&N type that fits inside the air-cleaner housing. But mighty few street engines come close to requiring more flow than provided by the OEM filter element.

The Vortec heads need 6 coolant bypass holes be drilled into each head when mounted on a 400 block. Don't forget this or you'll crack the block around the upper part of siamiesed section of the cylinder walls.

Bogie